The Slippery Elm tree (ulmus fulva) grows in the eastern part of the United States and Canada. The part of the tree that is used for medicinal purposes is the inner bark. The inner bark is ground into a powder and then combined with a crystalline substance to form a throat lozenge.

The original Thayers formula was first created in 1847, specifically for Opera Singers. Since it is Menthol-free, it is homeopathic compatible.